The present invention relates to novel metallocene compounds based on a transition metal (Groups 3-10 of the Periodic Table (IUPAC 1990)). The invention also relates to polymerization catalyst compositions comprising a metallocene compound selected from said metallocene compounds and an aluminoxane. Further, the invention relates to a process for polymerizing at least one ethylenically unsaturated monomer such as an olefin in the presence of a metallocene compound, selected from said metallocene compounds, and an aluminoxane.
Metallocene stands for metal complexes having at least one isocyclic or heterocyclic xcex7-cyclopentadiene ligand or at least one ligand structurally including isocyclic or heterocyclic xcex7-cyclopentadiene. Such an xcex7-cyclopentadiene ligand or ligand structurally including xcex7-cyclopentadiene is below called an xcex75 ligand, because all 5 cyclopentadienyl ring carbons are, without limiting the scope of protection, assumed to be essentially equally bound to the transition metal. Transition metals are elements with an incomplete d-shell in their atoms. They are metals of Groups 3-10 of the Periodic Table (IUPAC 1990). Aluminoxane stands for compounds having units of organometallic aluminium bound to oxygen.
Chiral bis(indenyl) ansa-metallocenes are well known catalyst components for polymerizations of alpha olefins. The performance of these metallocenes are different, depending on the metal used and the size and structure of the ligands, above all its xcex75 ligands. For the production of isotactic polypropene, C2-symmetric ethylene-bridged bisindenyl zirconocene dichloride can be regarded as a key structure. It was first reported by Brinzinger et al. in 1982 (Wild, F. R. W. P., Zsolnai, I., Huttner, G., Brintzinger, H. H., J. Organomet. Chem. (1982) 232:233). Syndiotactic polypropene was prepared in 1988 using CS-symmetric methylene-bridged fluorenyl cyclopentadienyl zirconocene dichloride. See Ewen, J. A., Jones, R. L., Razavi, A., Ferrara, J. D., J. Am. Chem. Soc. (1988) 110:6255.
Metallocenes having bulkier xcex75 ligands have also been prepared and investigated. Unsymmetric ethylene-bridged 7,9-diphenylcyclopent[a]acenaphthadienyl cyclo-pentadienyl zirconocene dichloride was used together with methylaluminoxane (MAO) for propene polymerization. It produces atactic polypropene with high activity. See Rieger, B., Repo, T., Jany, G., Polymer Bulletin 35 (1995) 78-94.
The above mentioned metallocenes are primarily suitable for the polymerization of polypropene. The successful production of polyethene, and in particular high molecular weight polyethene (molecular weight of the magnitude up to one million), using metallocenes of the above type, has not been reported. Thus, the purpose of the invention is to find a suitable metallocene for the production of high molecular polyethylene in good yields.
The above mentioned prior metallocenes are primarily suitable for the polymerization of linear or short chain branched polypropene. The successful production of long chain branched polypropene, using metallocenes of the above type, has not been reported. Thus, an additional purpose of the invention is to find a metallocene for the production of long chain branched polypropene in good yields.
The above purposes of the invention has now been achieved with a metallocene compound based on a transition metal (of Groups 3-10 of the Periodic Table (IUPAC 1990)), which metallocene compound is essentially characterized in that at least one of its xcex75 ligands comprises at least four fused rings including the xcex75 bound cyclopentadiene ring and that the sum of fused rings in all of its xcex75 ligands is at least 6.
Thus, it has been realized that a metallocene compound having more than a certain number fused rings in one and all of its xcex75 ligands give high molecular weight polyethene in good yields. It has also been found that such a metallocene gives vinyl terminated polypropene, which via its reactive vinyl group forms, or is able to form, a polypropene having long chain branches. These two technically relevant functional properties distinguish the metallocene compounds of the invention from e.g. the metallocene compounds of above mentioned Rieger, B., Repo, T., lany, G., Polymer Bulletin 35 (1995) 78-94.
In its widest scope, the present document claims metallocenes of transition metals (metals of Group 3-10 of the Periodic Table) having a certain minimum number of fused rings including the cyclopentadiene ring in one and all of its xcex75 ligands. However, according to a preferred embodiment of the invention, the metallocenes are based on transition metals of Groups 4-6, preferably Groups 4 and 5 of the Periodic Table (IUPAC 1990). Especially preferred transition metals are the Group 4 metals titanium, zirconium and hafnium, even more preferred zirconium and hafnium. Generally, the most preferred transition metal is zirconium.
According to the invention, the number of fused rings in at least one of the metallocene""s xcex75 ligands is at least four. The fused rings may be 5- and 6-membered rings, which are isocyclic or heterocyclic, for example containing up to 4 ring heteroatoms selected from O, N, S and P. By the terms xe2x80x9cisocyclicxe2x80x9d and xe2x80x9cheterocyclicxe2x80x9d is meant cyclic having only carbon ring members and cyclic having ring members of carbon and at least another element, respectively. The fused rings are preferably aromatic, but they can also be hydroaromatic, i.e. partially or completely hydrogenated (alicyclic). Typically, such xcex75 ligands are four ring xcex75 ligands, e.g. cyclopent[a]-as-indacenadienyl, cyclopent[a]-s-indacenadienyl, cyclopent[a]acenaphthadienyl, and five ring xcex75 ligands, e.g. cyclopent[d]-acephenathradienyl, cyclopent[a]aceanthradienyl.
According to a preferred embodiment of the invention, the xcex75 ligand of the metallocene comprising at least four fused rings is a ligand having the formula (I) 
wherein each same or different of groups R1-R9 is one of hydrogen, a halogen and an organic group having from 1 to 20 carbon atoms, or at least one pair of adjacent groups from R1-R9 form together an organic ring structure having from 5 to 20 carbon atoms, one of R7-R9 being optionally replaced by a bridge to another xcex75 ligand, and a indicates the xcex75 bound cyclopentadienyl ring of said xcex75 ligand comprising at least four fused rings; or is a hydroaromatic derivative ligand thereof.
Organic group or organic ring structure mean a group or ring structure, which is organic, i.e. is a carbon compound radical with the exception of radicals of non-hydrogen chalcogenides and their derivatives, salt-like and metallic carbides and metal carbonyls. A hydroaromatic derivative means a compound of similar ring structure but with the benzene rings partially or completely hydrogenated.
In the xcex75 ligand according to formula (I), R1-R6 are preferably hydrogen and, independently, one or two of R7-R9 are each independently a C1-C20 hydrocarbyl, preferably a C5-C20 hydrocarbyl, most preferably phenyl. Said ligand having the formula (I) is preferably a substituted or unsubstituted cyclopent[a]acenaphthtadienyl ligand or a hydroaromatic derivative thereof, preferably a 7,9-diphenylcyclopent[a]acenaphthtadienyl ligand.
It is advantageous, if in the metallocene compound, the number of said xcex75 ligands comprising at least four fused rings is 1 or 2.
The metallocene compound according to the invention can in addition to said xcex75 ligands comprising at least four fused rings have other ligands, as well. These other ligands can be xcex75 ligands comprising less than four fused rings, "sgr" (-bound) ligands, ligands of ionic nature and bridge ligands. A bridge is a bivalent atom or group which is bound to two moieties selected from the transition metall central atom and the ligands of the metallocene compound.
According to one embodiment of the invention, all xcex75 ligands of the metallocene compound are xcex75 ligands comprising at least four fused rings. The compound may, of course, also have other, non-xcex75 ligands such as halogens, hydrocarbyls and heteroatom bridge structures. According to another embodiment, the metallocene compound comprises a xcex75 ligand having less than four fused rings such as two fused rings, like substituted or unsubstituted, iso- or heterocyclic indene or tetrahydroindene, or three fused rings, like substituted or unsubstituted, iso- or heterocyclic fluorene or octahydrofluorene. The number of said xcex75 ligands having less than four fused rings is preferably 0 or 1.
As was said above, the claimed metallocene compound may have other than xcex75 ligands. According to an embodiment of the invention, the metallocene compound has at least one non-xcex75 ligand, which is one of hydrogen, a halogen, an organic group having from 1 to 10 carbon atoms or an organic group forming together with said transition metal a metallocyclic ring structure having from 4 to 20 carbon atoms. Preferably, the non-xcex75 ligand is one of a hydrocarbyl having from 1 to 10 carbon atoms or a halogen, most preferably one of methyl or chlorine. The number of said non-xcex75 ligands is preferably 1-3, more preferably 1 or 2, most preferably 2.
According to an embodiment of the invention, the claimed metallocene compound may have at least one bridge, which is a bivalent atom or a bivalent organic group having from 1 to 20 carbon atoms and which connects two of said xcex75 ligands or one of said xcex75 ligands and said transition metal. The bridge is preferably attached to the xcex75 bound cyclopentadiene ring of one or two of said xcex75 ligands.
According to one embodiment of the invention, said bridge is a bridge between two of said xcex75 ligands. Being so, it is preferably a silylene bridge having two organic substituents with 1 to 10 carbon atoms, e.g. two methyls, or an alkylene bridge having from 1 to 20 carbon atoms, e.g. ethylene. Most preferably, the bridge between two of said xcex75 ligands is an aromatically substituted alkylene bridge, most preferably a phenylethylene bridge.
According to another embodiment of the invention, said bridge is bridge between one of said xcex75 ligands and said transition metal. Being so, it preferably comprises, connected in succession, a first bivalent group of the formula xe2x80x94NRxe2x80x94, xe2x80x94PRxe2x80x94, xe2x80x94Oxe2x80x94, or xe2x80x94Sxe2x80x94, and a second bivalent hydrocarbylene group having 1-20 carbon atoms, said first bivalent group most preferably being bound to said transition metal.
The number of said bridges between two of said xcex75 ligands or one of said xcex75 ligands and said transition metal is preferably 0, 1 or 2, more preferably 0 or 1, most preferably 1.
According to a conclusive preferable embodiment of the present invention, said metallocene compound has 1 or 2 of said xcex75 ligands having at least four used rings, 0 or 1 of said xcex75 ligands having less than four fused rings, 1, 2 or 3 of said non-xcex75 ligands and 0 or 1 of said bridges.
Advantageously the claimed metallocene compound has the formula (II)
(ACp)g(BCp)hMnXiYjZkxe2x80x83xe2x80x83(II)
wherein: ACp or each same or different ACp is an xcex75 ligand of the formula (I) 
wherein each same or different of groups R1-R9 is one of hydrogen, a halogen, an organic group having from 1 to 20 carbon atoms or at least one pair of adjacent groups from R1-R9 form together an organic ring structure having from 5 to 20 carbon atoms, one of R7 to R9 being optionally replaced by a bridge Z to another xcex75 ligand ACp or BCp, and a indicates an xcex75 bound cyclopentadienyl ring, or a hydroaromatic derivative thereof; BCp or each same or different BCp is one of a mono- or polysubstituted, fused or non-fused, iso-(homo-) or heterocyclic, indenyl xcex75 ligand or fluorenyl xcex75 ligand, or a hydroaromatic derivative thereof; M is a transition metal of one of Groups 4 and 5 of the Periodic Table (IUPAC 1990) and bound to said ligand or ligands ACp and BCp in at least a xcex75 bonding mode; X or each same or different X is bound to M and is one of hydrogen, a halogen, an organic group having from 1 to 20 carbon atoms or two X form together with said M a metallocyclic ring structure having from 4 to 20 carbon atoms; Y is a bridge atom or bridge organic group having from 1 to 20 carbon atoms between one of said ligands ACp or BCp and said transition metal M; Z is a bridge atom or bridge group between two of said ACp or BCp ligands; g is 1-4; h is 0-3; i is 1-4; j is 0-2; k is 0-2; g+h greater than 1 and n=valence of M=g+h+i+j.
A particularly advantageous metallocene compound of the invention has the formula (IIIa) or (IIIb): 
wherein: each same or different of R1 to R9 and R1xe2x80x2 to R9xe2x80x2 is one of a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms or at least one pair of adjacent groups of R1-R9 form together an organic ring structure having from 5 to 20 carbon atoms; M is a four-valent transition metal of Group 4 of the Periodic Table (IUPAC 1990); each same or different X is bound to M and is one of hydrogen, a halogen, an organic group having from 1 to 20 carbon atoms or two X form together with said M a metallocyclic ring structure having from 4 to 20 carbon atoms; and bridge Z is a bivalent atom or bivalent group.
In the metallocene compounds of formulas (IIIa) and (IIIb), the four-valent transition metal is preferably zirconium or hafnium, most preferably zirconium. X is preferably a halogen, most preferably chlorine, or preferably an alkyl having from 1 to 4 carbon atoms, most preferably methyl. At least one of R7, R7xe2x80x2, R9, and R9xe2x80x2 is advantageously a substituted or unsubstituted cyclic organic group having from 5 to 20 carbon atoms, most advantageously a substituted or unsubstituted aromatic group, most preferably a phenyl group. According to an embodiment, R7, R7xe2x80x2, R9, and R9xe2x80x2 are phenyl groups and, preferably, groups R1 to R6 and R1xe2x80x2 to R6xe2x80x2 are hydrogens.
The bridge Z of the metallocene compounds of formulas (IIIa) and (IIIb) is according to an embodiment a silylene bridge having two organic substituents with 1 to 10 carbon atoms, for example two methyl susbtituents, or an alkylene bridge having from 1 to 20 carbon atoms, e.g. an ethylene bridge. Most preferably, the bridge Z is an alkylene bridge substituted with a substituted or unsubstituted cyclic organic group having from 5 to 20 carbon atoms, preferably a substituted or unsubstituted aromatic group, most preferably a phenyl group. Advantageously, the bridge Z is phenyl ethylene.
The metallocene compounds of formulas (IIIa) and (IIIb) are, for example, {[1-(7,9-diphenylcyclopent[a]acenaphthadienyl)-1-phenyl-2-(7,9-diphenylcyclopent[a]acenaphthadienyl)]ethane}zirconium dichloride having the formula (IV): 
The metallocene compounds of formulas (IIa) and (IIb) may also advantageously be {[1-(7,9-diphenylcyclopent[a]acenaphthadienyl)-1-phenyl-2-fluorenyl]ethane}zirconium dichloride having the formula (V): 
The metallocene compounds of formulas (IIIa) and (IIIb) may also advantageously be [bis(7,9-diphenylcyclopent[a]acenaphthadienyl)]zirconium dichloride having the formula (VI): 
The metallocene compounds of formulas (IIIa) and (IIIb) may further advantageously be [bis(7,9-diphenylcyclopent[a]acenaphthadienyl)]hafnium dichloride having the formula (VII): 
The present invention also relates to a process for the preparation of a metallocene of said metallocene compound. In the process there are the steps of.
(a) forming of an alkali metal salt of at least one cyclopentadiene derivative comprising at least four fused rings including a cyclopentadiene ring,
(b) forming said metallocene by reacting said alkali metal salt with a transition metal halide comprising at least two halogens.
If the metallocene compound comprises a substituted or unsubstituted ethylene bridge between two xcex75 ligands, said metallocene is preferably prepared according to the following reaction scheme: 
wherein each M is independently an alkali metal, preferably lithium, R is hydrogen or a hydrocarbyl group having 1-20 carbon atoms, preferably phenyl, each X is independently a halogen, preferably chlorine, Cp1 is a cyclopentadiene derivative comprising at least four fused rings including a cyclopentadiene ring, preferably 7,9-diphenylcyclopent[a]acenaphthadienyl and Cp2 is the same or different Cp1 or a cyclopentadiene derivative comprising less than four, preferably two or three fused rings including a cyclopentadiene ring, preferably one of 7,9-diphenylcyclopent[a]acenaphthadienyl, indenyl, tetrahydroindenyl, fluorenyl and octahydrofluorenyl, preferably 7,9-diphenylcyclopent[a]acenaphthadienyl or fluorenyl, MDA is an alkalimetal salt of a dialkyl amine, preferably a lithium salt of diisopropyl amine, and Tr is a transition metal, preferably Zr or Hf
In addition to said metallocene compound and its preparation process, the invention also relates to an olefm polymerization catalyst composition, which comprises said metallocene compound and an activator thereof. The activator may be any compound in the art which activates metallocenes for polymerization, including alkylalumimum compounds, alkyl aluminoxanes such as methyl aluminoxane, tetraisobutyl aluminoxane (cage structure) and hexaisobutylaluminoxane (cage structure). It may also be a Lewis or protic acids such as B(C6H5)3 or [PhNMe2H] +B(C6F5)4xe2x88x92, which generates cationic metallocenes with compatible non-coordinating anions in the presence or absence of alkylaluminium compounds.
Preferred activators of the claimed polymerization catalyst composition are alkyl aluminoxanes having one of the following formulas (IX and X): 
wherein: each Rxe2x80x3 is the same or different and is an organic group having from 1 to 20 carbon atoms, preferably an alkyl group having from 1 to 10 carbon atoms; and p is an integer between 1 and 40.
A particularly preferred aluminoxane activator is methyl aluminoxane.
Particularly important is the claimed process for polymerizing at least one ethylenically unsaturated monomer. Such a monomer may be a monoethylenically unsaturated compound, e.g. an olefin such as ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, isobutene, 3-methyl-1-butene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene and vinylcyclohexane, a vinyl compound such as vinyl acetate, vinyl chloride, vinyl fluoride, a styrenic compound such as styrene, xcex1-methyl styrene and vinyl styrene, an acrylic monomer such as methyl acrylate, methyl methacrylate and acrylonitrile. The monomer may also be a polyethylenically unsaturated compound such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and chloroprene, as well as dicyclopentadiene, 4-ethyl-2-norbornene and 1,4-hexadiene.
According to the invention, the monomer is polymerized in the presence of a metallocene compound described above and preferably in the presence of a catalyst composition (metallocene compound plus activator) as described above. Because the aim of the invention was to find a metallocene compound useful for the polymerization of ethene to high molecular weight polyethene, the process of polymerizing ethene to high molecular weight polyethene is particularly important and preferred. By high molecular weight polyethene is meant polyethene having a molecular weight of about 200,000 g/mol to about 2,000,000 g/mol, preferably about 1,000,000 g/mol.
Another advantage of the claimed metallocene compound and catalyst composition is that they can be used to prepare vinyl terminated polypropene molecules. Without limiting the scope of protection, vinyl termination is believed to take place through xcex2-elimination of methyl at the active sites of the catalyst composition. The vinyl terminal groups of the polypropene molecules are reactive and are during continuous polymerization or separate post-polymerization attached to the polypropene macromolecular chains, whereby long-chain branched polypropene is formed. Such a preparation of long-chain branched polypropene using said metallocene or said catalyst composition is also claimed.